I. Field of the Invention
The present invention relates generally to spinal surgery, and more particularly to devices for fusing adjacent spinous processes to stabilize the vertebral segment associated with the particular spinous processes.
II. Discussion of the Prior Art
The human spinal column is made up of two basic components, vertebrae (bone) and intervertebral discs (gel-like cushions that absorb pressure and prevent vertebrae from rubbing together). A number of vertebrae and intervertebral discs stack together to form a column that provides support and structure for the body while still allowing a large degree of motion and flexibility. The spinal column also serves to protect the spinal cord (a bundle of nerves linking the brain to the rest of the body) that runs through an opening formed in the center of the column. A pair of nerve roots exit the spinal column at each level through spaces formed between the vertebrae. Various traumatic events and degenerative conditions may result in undesirable motion or changes in disc height, both of which may cause chronic pain for the affected individual. The pain is generally caused when changes in disc height and improper motion allow adjacent vertebrae to impinge upon exiting nerve roots. The degree and treatment of pain varies by individual but in many instances the pain can be disabling and uncontrollable by non-invasive means, leaving surgery as the only viable option. Generally in such a case, two or more vertebrae are fused together, employing various instrumentation and methods to correct disc height and prevent improper movement of the vertebrae while fusion occurs, thereby eliminating or at least reducing the pain of the affected individual.
While there are a variety of systems and methods for effecting spinal fixation while fusion occurs, one of the more common methods involves securing pedicle screws into the pedicles of the two or more adjacent vertebrae to be fixed. The challenge in this method is securing the pedicle screws without breaching, cracking, or otherwise compromising the pedicle wall, which may occur if the screw is not properly aligned with the pedicle axis. If the pedicle (or more specifically, the cortex of the medial wall, lateral wall, superior wall and/or inferior wall) is breached, cracked, or otherwise compromised, the patient may experience pain or neurological deficit due to unwanted contact between the pedicle screw and delicate neural structures, such as the spinal cord or exiting nerve roots. This may necessitate revision surgery, which is disadvantageously painful for the patient and costly, both in terms of recovery time and hospitalization.
The present invention is directed to overcome one or more shortcomings encountered with current fixation devices and systems.